This invention relates in general to transformer coil assemblies having concentrically wound coils, and more particularly to a method of making such coil assemblies.
Small transformers used for power supplies, control systems and other various purposes are commonly constructed with concentric primary and secondary coils wound on concentrically arranged bobbins which are assembled with a laminated magnetic core. Examples of transformer coil assemblies employing such a telescoped bobbin arrangement may be found in Klatte et al. U.S. Pat. No. 3,403,366 and Johnston et al. U.S. Pat. No. 3,652,968, disclosures of which are incorporated herein by reference. In the past, coil assemblies of this telescoped bobbin construction have been more costly than desired in that they required several independent fabricating steps such as molding of the bobbins, winding of the coils on the bobbins, forming or attaching leads for the coils, and assembly of one bobbin into another. It is obvious that the separate bobbin molding operations, the separate coil winding operations and other fabricating steps with multiple handlings of the bobbin are time consuming and costly.